Method of softening the ends of electrodes and other carbon articles.



J. W. BROWN.

METHOD OF SOFTENING THE ENDS OF ELECTRODES AND OTHER CARBON ARTICLES.

APPLICATION FILED JUNE 10 1912.

Patented Jan. 13, 1914.

2 SHEETS-SHEET 1.

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INVENTOR JOHN w. BROWN BY OQL WITNESS ES ATTORNEY J. W. BROWN.

METHOD OF SOFTENING THE ENDS OF ELECTRODES AND OTHER. CARBON ARTICLES.

APPLICATION FILED JUNE 10, 1912.

1,084,129. Patented Jan. 13, 1914 2 SHEETSSHEET 2.

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PIBJB. I 23 W WITNESSES INVENTOR W JOHN w. BROWN 1 Method of Softening the V and other Carbon Articles, of which the folelectrical contact "is made.

I M ED STATES PATENT-OFFICE.

' Jomv w. BBOWN, or Laxnwoon, 01110, AssIGNon r0 NATIONAL cannon comramr,

CLEVELAND, OHIO, A CORPORATION OF NEW JERSEY.

METHOD OF SOFTENIDlG THE OF ELECTRODES AND OTHER CARBON ARTICLES.

Specification of Letters Patent.

Application mes June 10, 1912. Serial No. 702,098.

- Patented Jan. 13, 1914.

To all whom it may concern Be it known that I, JOHN Cuyahog'a, in the State of Ohio, have invented new and useful Im rovements in the nds of Electrodes lowing is a clear and exact description.

This invention relates to a' method of" softening the ends of furnace electrodes so that a threaded connection can be'made. The method is not, however, limited to this particular application as it can be used to locally soften any carbon article for any purpose. l p

It is frequently necessary to join carbon articles together in such a wayv that good An instance of this is in furnace electrodes. When-a furna'ce electrode had been consumed to such an extent that it no longer projected sufficientl into the furnace, it was formerly the pr'actlce' to throw away the stub end. This .stu-b extended through the thick furnace wall sufliciently to enable a proper contact to be made with the bus bars, and hence it was of sufiicient length to entail considerableloss when it was thrown 'on the scrap tire electrode, avo ding the lossthat form- 'erly resulted from throwing away the stub ends. Furnace electrodes are baked very hard, so that practically the onl way that threads can be cut'on'the ends is y means of small emery wheels. Before the threads can be cut in this Way, however, it is necessary tochi awaythe outside portions to form a sachet in'one end and a tenon -0r dowel on the other end. That method of forming the screw connections is slow and expensive.

It is well known that graphite electrodes W. BROWN, a resident of Lakewood, in the county of are soft and easily worked,'and when furnace electrodes are made of graphite there is very littletrouble in machining the ends very short time. By using current densities of approximately 5000' amperes per square inch have been able to graphitize carbon in 20 seconds. This quick graphitization of carbon enables me to carry out my methodv of softening certain parts of furnace electrodes in a very shorttimc, while the remaining parts are substantial unchanged.

Referring to the drawings; resents more or less diagrammatically an arrangement for softening a core in the end of a furnace electrode. .Fi 2 is a cross section on the line A'A of ig. 1. Fig. 3 is a sectional view'of an. arrangement for softening the outer shell of the end of the electrode. Fig. 4is a sectiontaken on the line BB ofFig. 3. Fig. 5 is an arran ement for softening" the, core in one end of t e electrode at the same time that the outer shellof the other e'nd'of the electrode is being softened. Fig. dis a sectional elevation of an arrangement for treating anumber of electrodes at the same time. Fig. 7 is a view of the box shown in'Fig. 6. Fig. Sis a longitudinal section ;of a furnace electrode showing a threaded socket on one .and a igure 1 repthreaded tenon on the other. Fig. 9 is a view of the resistor to be used with rec- "tangular electrodes. Fig. 10 is across section of another modification of a terminal electrode to be used in the process. Fig. 11 isa cross section of another modification of a terminal electrode. Fig. 12 is a sectional view of a modified form of terminal electrode. Fig. 13 is a sectional view of a somewhat siinilar modification to that shown in Fig. 12. Fig. 14 shows a modified form of reslstor adapted to slip over the end ofthe electrodes. Fig. is a sectional view taken on the line BB of Fig. 14. Fig. 16 is a softened. The resistor 2, approximately.

the'size and shape in cross section of the part to be softened, is placed between the electrode 1 and another electrode 3. The electrical connections are made to the electrodes 3 and 1, diagrammatically shown at 4t and 5. A high current is then passed through the electrodes and ,the resistor. The density may be of any desired value, but'I have found that the best results are obtained when using currents of densities varying between. 500 and 5000 amperes per. squareinch. Substantially all the current is concentrated inside the central part of the electrode 1 and this part will be quickly heated to a' high temperature, while the remainingpart of'the electrode 1, will not be heated to such an extent, since the current spreads over the entire section of it. The contact between the resistor and the electrode will have a comparatively high resistance and a great amount of heat will be developed there. The radiation of this heat into the central core of the electrode end, together with that developed in the core by the current is concentrated therein, and will soon graphitize 0r soften this part while the remainder Will not be graphitized. This process results in a saving of electrical energy as only enough energy is required to graphitize the part within the dotted line 6.

In Fig. 3 I have shown how the outer shell of the electrode 1 may be softened at one end. The electrode is circular and hence the resistor 7 is circular as is shown in Fig. 4. This resistor will have substantially the same cross sectional area as the part to be softened on the electrode 1. The current is concentrated in the outer shell 8, and the heat developed in this part of the electrode, aided by the heat from the resistor contact, quickly converts it into graphite while the remainder is substantially unchanged.

In Fig. -5 I have shown an arrangement whereby a softened core may be made in one end of the electrode 1 at the same time that the softened. shell is made in the other end of the electrode. This arrangement is the combination of those shown in Figs. 1 and 3. Since the contact resistance causes a great amount of heat to be developed it is advantageous to use a plurality of short resistors, and such have been shown in Fig. 5. I have found it advantageous to apply presand machined and screw threaded.

sure to the ends of the electrodes 33, and this is diagrammatically indicated by screws 99, the arrows P, P indicating the direction of pressure. However, my method is not limited to the use of pressure as it can be carried out by merely placing the resistors in contact between an electrode to be treated andthe terminal electrodes.

In Fig. 6 a plurality of electrodes are spaced apart and the spaces are bridged by a plurality of resistors. The current then traverses the whole in series. This arrangement permits the use of a higher terminal voltage, which is an advantage. The series arrangement is the more efficient as the losses in the external circuit are no greater than when only one electrode is treated.

In Fig. 7 is shown a box 15 made of some heatresisting material such as transite board. This box is first filled with crushed charcoal or some other heat insulating material to the depth of several inches. The electrodes 1 are then placed on the charcoal and properly spaced. The, ring sections 7 are then placed in alternate spaces. The

remainingspaces are partially filled with crushed charcoal and the sections 2 placed on top. The terminal electrodes 3, 3 are then forced against the'carbon plates 16, t0 firmly clamp" the arrangement together and the box 15" is I then entirely filled with crushed charcoal to retain the heat. The current is then turned on and in a short time the local parts will be softened as previously described.

In Figs. 10 and 11, I have shown modifications where the resistors are formed integral with the terminal electrodes. On the electrode 10 a tenon 12 is formed. The

cross sectionalform and area of the tenon should be substantially the same as' that of the core to be softened. The terminal electrode' 11 has a shell 13 similar to the resistor 7 in Figs. 3 and 5. The cross sectional shape and area .of this shell should correspond with that of the part to be softened.

In Fig. 8 the electrode 1 is shown after having been locally softened by my process T e right hand end of this electrode is shown in cross section to properly show the screw threaded socket.

In Fig. 9 the resistor 14 is shown rectangular in cross section. This form of resistor would be used to soften the outer shell of a rectangular electrode. It will be understood that the shape of the resistor will depend upon that of the part to be softened.

In Fig. 12 the electrode 1 is first hollowed out as shown, before it is baked. Very little. work is required to dothis while the electrode is green. The terminal electrode 3 is placed in a vertical position, as shown,

and the terminal electrode 3 is inserted, but

in the space around the electrode 1.

In order to confine the current where it is needed theelectrode 3 may rest on a block 18 of charcoal which is substantially a non conductor of electricity.v This block is placed in the cavity before the terminal electrode is placed therein.

In Fig. 13 the male and fema le ends of the electrodes 1-- are cut as shown, while 1 they are green and then they are softened by theelect-ric treatment. The tenon may be softened by means of the resistor rings while the socket may be softened by using the means shown in Fi 12 previously described. A resistor bloct' 19 resting against the non-conducting blocks 18 forms part ,of the electric circuit at the junction of the two electrodes. also flow directly from one electrode through the granular material 17 to the other electrode. The entire current, however, must enter and leave the surface of .thesockets through the granular material and at these surfaces the contact resistance causes a greatamount of heat to be generated, which together with the heat developed in the part 6 soon softens this part. Instead of a charcoal block 17 being used, a 'carborundum block can .be utilized pro- 1 viding the temperature is not carried too high.

' In Fig. 14 special shaped resistors are shown for softening the carbon on the male connection. The resistors may be made in two or more sectors if desired. The current enters the electrode ends at the outer sur face, and hence the heat caused by the contact resistance is most desirably located. In Fig. 15 the resistor is shown'in cross section, the section being taken on the line BB of Fig. 14.

In Fi 16 the resistor 21 is shown composed 0 only one part; The absence of the central dividing contact surface causes less heat to be developed, butthis type of resistor might be-more convenient to manipu I late.

In Fig. 18 the resistor is shown asbeing composed of a plurality of concentric sleeves. The plurality of contacts will increase the heat.

In'Fig. 19 the resistor is composed of a plurality of rings 22 and a plurality of rings 23, the latter having a greater radial thickness. vThe electrodes 1 make a close fit through/the rings 22 and abut against the rings 23. v

In Fig. 20V 21. different arrangement is shown. The resistor 20 is shaped similarly to that in Fig. 12, but it is made larger. The central bore 23 makes a snug fit with the ends of the electrodes 1. The ends are not in contact with each other, however.

Part of the current will current is compelled to leave and enter through the outer surfaces of the electrode ends and the heat developed there is intense.

\ The arrangements shown in Figs. 10, 12-, 14, 16, 18, 19 and 20 are intended to be used to soften the arts on the male end of the electrodes. hese arrangements, as are those shown in all the other figures, are intended to be coupled up appropriately in some box-form as is shown in Fi 6.

My process could be carrier? out with many different forms of apparatus, and since they form no art 1 of the invention claimed in this appllcation, the apparatus has been shown only in diagrammatic form. In my application Serial No. 695,354- of May 6th, 1912, I have disclosed a special type of furnace that would be well suited to carry out this process. V

It is not necessary to carry the tempera two high enough to convert the local parts into graphite. I have found that carbon when heated up to temperatures varying between 1500 and 2200 degrees centigrade becomes soft and appears to be changed into an allotropic form. I call this form superbaked carbon. This form, while not so soft as graphite, is a great deal softer than ordinary 'hard baked carbon and is readily machined. This process therefore can give satisfactory results if thetem eratures are.

garlried no higher than the limits just speci- Having claim is: 1

1. Themethod of softening-a part of the end of an electrode which consists in placmg a resistor having less cross section than the electrode end in engagement therewith, 1

described. my invention what I and passing an electrode current through stantially all of it to traverse said part of the end. r a

The method of softenin -the outer part. of the end of an electrode w ich consists in placing a shell resistor in contact :with the end thereof, and assing an electric current through the shell and the electrode.

4. The method of softening the outer part of the end of an electrode which consists in sending a currenttherethrough and causing substantially I all of it to flow through the said outer shell. f

5. In apparatus for locally softening car.- bon articles, a carbon resistor havingtwo central bores, one being of greater diameter than theother, whereby. an internal shoulder is formed adapted to abut against the end of the article to be softened.

' 6. In apparatus for locally Softening carbon art1c1es,a resistor composed of a plu- In testimony whereof I have hereunto slgned my name.

JoHN W. BROWN- 5 rality of carbon sleeves, the inner sleeve be- Witnesses: 7 mg adapted to receive the ends of the ar- 1 J. E. WAsmiUnN,

I. J. ADAMS.

ticles to be softened.

Corrections in Letters Patent No. 1,084,129.

It is hereby certified that in Letters Patent No. 1,084,129, granted January 13, 1914, upon the application of John Ws Brown, of Lakewood, Ohio, for an improve- 0 ment in Methods of Softening the Ends of Electrodes and Other Carbon Articles,

w errors appear in the printed specification requiring correction as follows: Page 3,

line 110, for the'word electrode read electric; same page, line 126, for the word shell read part; and that the said Letters Patent should beread with these corrections therein that the same may conform to the record of the case in the Patent Oflice. I

Signed and sealed this 3rd day of February, A. D., 1914.

I J. T. NEWTON,

Acting Commissioner of Patents; 

